IPhone storage issues

Hi so I have a iPhone 6s, with 32 GB storage. However since resetting my phone after it got fixed, something called 'system' is taking up 29GB of that 32GB storage. I can barely use my phone, can't use emails, I only have about 7 apps whereas before I never had an issue. Any ideas? I've tried everything online to get rid of it

Can i pay for a Straight talk Iphone XR in 3 big payments instead of a long payment plan?

I'm new to having payment plans to pay off a phone and I was wondering: Can i pay for a straight talk Iphone XR in 3 big payments instead of a long drawn out payment plan? I would like to pay the payments in payments of $250 each plus the phone service bill instead of paying for the phone little by little over 2 years. Also I was wondering: If i can do this, how do i make the payments? Do i make payments online, in-store, or what? I'm new to this, so sorry for all the questions